HR: 1330h
AN: P12B-1059    [PDF]
TI: Thin Elastic Shell Flexure Models of Possible Ocean Basins on Mars: Preliminary Analysis
AU: * Ghent, R R
EM: ghentr@nasm.si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Musem, Smithsonian Institution, Washington, DC 20560 United States
AU: Leverington, D W
AF: Center for Earth and Planetary Studies, National Air and Space Musem, Smithsonian Institution, Washington, DC 20560 United States
AU: Dombard, A J
AF: Department of Earth and Planetary Sciences, Washington University, Saint Louis, MO 63130 United States
AB: Hypothesized ancient Martian water bodies contained in large basins such as Argyre, Hellas, and the northern lowland plains would have represented massive surficial loads. Earth analogs suggest that the magnitudes of lithospheric displacements due to water loading would have varied spatially within and around affected basins, causing basin geometries and strandline positions to change over time and potentially influencing tributary base levels and the positions of proximal basin divides and outlets. It is likely that lithospheric deflection would have caused shoreline areas proximal to deep regions to subside (and subsequently rebound) more than those near shallow regions. An Airy isostatic approximation provides an end-member estimate of the magnitude of the effect of water loading and indicates that the shoreline elevation of a water body of a given volume can differ significantly (up to hundreds of meters) depending on whether or not the water load is included in the isostatic balance. Such a model does not directly address differential subsidence or rebound because it ignores the flexural strength of the lithosphere; however, more appropriate two-dimensional flexure calculations support the notion that sets of Martian strandlines should reflect variations in loading. Thus, current searches for geological evidence of large ancient Martian water bodies (liquid or solid) should not necessarily involve the assumption that water-marginal features of common age will collectively lie in horizontal planes today. We report on work in progress involving analytical thin elastic shell flexure models in spherical geometry to investigate regional effects of loading Mars' lithosphere by large water bodies by including a water load in the flexure equations. We use this preliminary scheme to estimate differential rebound magnitudes for various basins. Our ultimate goal is to calculate the flexural deflection for actual Martian basins loaded by water (or ice) and to combine this long-wavelength deflection with the MOLA-derived topography in order to analyze relationships between predicted horizons and the positions of outlet divides, tributary base levels, or possible ancient strandlines.
DE: 3210 Modeling
DE: 5455 Origin and evolution
DE: 5475 Tectonics (8149)
DE: 5499 General or miscellaneous
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting